Investigation of uniaxially drawn polyethlene by positron annihilation

Abstract

Positron annihilation lifetime spectra are measured in uniaxially drawn polyethylene (PE) at room temperature as function of deformation ϵ from 0 to 190%. The positron annihilation parameters are very sensitive to the microstructural changes of PE during the drawing process. In the elastic stage (ϵ = 0 to 20%), the amount and size of voids in amorphous regions and the size of defects in crystalline regions increase drastically with increasing deformation and reach a maximum at the yield point. In the strain softening stage (ϵ = to 40%), the fractional free volume f is nearly constant. When ϵ < 40%, i.e. in the plastic stage, the fractional free volume f continuously decreases, which shows that the degree of crystallinity increases owing to the orientation of chains and strain‐induced crystallization. continuously decreases, which shows that the degree of crystallinity increases owing to the orientation of chains and strain‐induced crystallization.

Investigation of the Effects of Temperature and Strain on the Damping Properties of Polycarbonate/Multiwalled Carbon Nanotube Composites

“…According to our previous study, when the strain is very small, the free volume and the fractional free volume increase with the strain. However, when the strain increases further, they all decrease with increasing strain.…”

Subnanometer Ion Channel Anion Exchange Membranes Having a Rigid Benzimidazole Structure for Selective Anion Separation

“…In addition, the polymer with the larger void free-volume has the longer long-lifetime, and the relative peak intensity ( I 3 ) is proportional to the number of voids. f represents the relative free-volume content within the membrane matrix. ,− Figure b shows the free-volume distribution. Therein, we can see that δ 3 of 12A-PAES-sIM is 2009 ps and δ 3 of IM-PAES-sIM is 2014 ps, which are in accordance with the average void free-volumes in 12A-PAES-sIM and IM-PAES-sIM of about 88 and 101 Å 3 , respectively.…”

“…Free-volumes of as-prepared dried AEMs were measured by a positron annihilator (DPLS 3000), and the spectrum software used was MELT 4.0. The free-volume was calculated according to equation as follows: where f (%) is the relative free-volume fraction, FV (nm 3 ) is the average free-volume size, and the I 3 (%) is the relative integral of the long-lifetime peak.…”